pythonGH-126985: move pyconf.cfg detection from site to getpath

Signed-off-by: Filipe Laíns <lains@riseup.net>

Lib/test/test_getpath.py

@@ -92,8 +92,8 @@ def test_venv_win32(self):
         ])
         expected = dict(
             executable=r"C:\venv\Scripts\python.exe",
-            prefix=r"C:\Python",
-            exec_prefix=r"C:\Python",
+            prefix=r"C:\venv",
+            exec_prefix=r"C:\venv",
             base_executable=r"C:\Python\python.exe",
             base_prefix=r"C:\Python",
             base_exec_prefix=r"C:\Python",
@@ -339,8 +339,8 @@ def test_venv_posix(self):
         ])
         expected = dict(
             executable="/venv/bin/python",
-            prefix="/usr",
-            exec_prefix="/usr",
+            prefix="/venv",
+            exec_prefix="/venv",
             base_executable="/usr/bin/python",
             base_prefix="/usr",
             base_exec_prefix="/usr",
@@ -371,8 +371,8 @@ def test_venv_changed_name_posix(self):
         ])
         expected = dict(
             executable="/venv/bin/python",
-            prefix="/usr",
-            exec_prefix="/usr",
+            prefix="/venv",
+            exec_prefix="/venv",
             base_executable="/usr/bin/python3",
             base_prefix="/usr",
             base_exec_prefix="/usr",
@@ -404,8 +404,8 @@ def test_venv_non_installed_zip_path_posix(self):
         ])
         expected = dict(
             executable="/venv/bin/python",
-            prefix="/path/to/non-installed",
-            exec_prefix="/path/to/non-installed",
+            prefix="/venv",
+            exec_prefix="/venv",
             base_executable="/path/to/non-installed/bin/python",
             base_prefix="/path/to/non-installed",
             base_exec_prefix="/path/to/non-installed",
@@ -435,8 +435,8 @@ def test_venv_changed_name_copy_posix(self):
         ])
         expected = dict(
             executable="/venv/bin/python",
-            prefix="/usr",
-            exec_prefix="/usr",
+            prefix="/venv",
+            exec_prefix="/venv",
             base_executable="/usr/bin/python9",
             base_prefix="/usr",
             base_exec_prefix="/usr",
@@ -652,8 +652,8 @@ def test_venv_framework_macos(self):
         ])
         expected = dict(
             executable=f"{venv_path}/bin/python",
-            prefix="/Library/Frameworks/Python.framework/Versions/9.8",
-            exec_prefix="/Library/Frameworks/Python.framework/Versions/9.8",
+            prefix=venv_path,
+            exec_prefix=venv_path,
             base_executable="/Library/Frameworks/Python.framework/Versions/9.8/bin/python9.8",
             base_prefix="/Library/Frameworks/Python.framework/Versions/9.8",
             base_exec_prefix="/Library/Frameworks/Python.framework/Versions/9.8",
@@ -697,8 +697,8 @@ def test_venv_alt_framework_macos(self):
         ])
         expected = dict(
             executable=f"{venv_path}/bin/python",
-            prefix="/Library/Frameworks/DebugPython.framework/Versions/9.8",
-            exec_prefix="/Library/Frameworks/DebugPython.framework/Versions/9.8",
+            prefix=venv_path,
+            exec_prefix=venv_path,
             base_executable="/Library/Frameworks/DebugPython.framework/Versions/9.8/bin/python9.8",
             base_prefix="/Library/Frameworks/DebugPython.framework/Versions/9.8",
             base_exec_prefix="/Library/Frameworks/DebugPython.framework/Versions/9.8",
@@ -734,8 +734,8 @@ def test_venv_macos(self):
         ])
         expected = dict(
             executable="/framework/Python9.8/python",
-            prefix="/usr",
-            exec_prefix="/usr",
+            prefix="/framework/Python9.8",
+            exec_prefix="/framework/Python9.8",
             base_executable="/usr/bin/python",
             base_prefix="/usr",
             base_exec_prefix="/usr",

Misc/NEWS.d/next/Library/2024-11-18-23-42-06.gh-issue-126985.7XplY9.rst

@@ -0,0 +1,3 @@
+When running under a virtual environment with the :mod:`site` disabled (see
+:option:`-S`), :data:`sys.prefix` and :data:`sys.base_prefix` will now point
+to the virtual environment, instead of the base installation.

Modules/getpath.py

@@ -640,11 +640,18 @@ def search_up(prefix, *landmarks, test=isfile):
 
 
 # For a venv, update the main prefix/exec_prefix but leave the base ones unchanged
-# XXX: We currently do not update prefix here, but it happens in site.py
-#if venv_prefix:
-#    base_prefix = prefix
-#    base_exec_prefix = exec_prefix
-#    prefix = exec_prefix = venv_prefix
+if venv_prefix:
+    base_prefix = prefix
+    base_exec_prefix = exec_prefix
+    prefix = exec_prefix = venv_prefix
+
+
+# After calculating prefix and exec_prefix, use their values for base_prefix and
+# base_exec_prefix if they haven't been set.
+if not base_prefix:
+    base_prefix = prefix
+if not base_exec_prefix:
+    base_exec_prefix = exec_prefix
 
 
 # ******************************************************************************
@@ -679,7 +686,7 @@ def search_up(prefix, *landmarks, test=isfile):
         # QUIRK: POSIX uses the default prefix when in the build directory
         pythonpath.append(joinpath(PREFIX, ZIP_LANDMARK))
     else:
-        pythonpath.append(joinpath(prefix, ZIP_LANDMARK))
+        pythonpath.append(joinpath(base_prefix, ZIP_LANDMARK))
 
     if os_name == 'nt' and use_environment and winreg:
         # QUIRK: Windows also lists paths in the registry. Paths are stored
@@ -714,13 +721,13 @@ def search_up(prefix, *landmarks, test=isfile):
     # Then add any entries compiled into the PYTHONPATH macro.
     if PYTHONPATH:
         for p in PYTHONPATH.split(DELIM):
-            pythonpath.append(joinpath(prefix, p))
+            pythonpath.append(joinpath(base_prefix, p))
 
     # Then add stdlib_dir and platstdlib_dir
-    if not stdlib_dir and prefix:
-        stdlib_dir = joinpath(prefix, STDLIB_SUBDIR)
-    if not platstdlib_dir and exec_prefix:
-        platstdlib_dir = joinpath(exec_prefix, PLATSTDLIB_LANDMARK)
+    if not stdlib_dir and base_prefix:
+        stdlib_dir = joinpath(base_prefix, STDLIB_SUBDIR)
+    if not platstdlib_dir and base_exec_prefix:
+        platstdlib_dir = joinpath(base_exec_prefix, PLATSTDLIB_LANDMARK)
 
     if os_name == 'nt':
         # QUIRK: Windows generates paths differently
@@ -750,7 +757,8 @@ def search_up(prefix, *landmarks, test=isfile):
 
 # QUIRK: Non-Windows replaces prefix/exec_prefix with defaults when running
 # in build directory. This happens after pythonpath calculation.
-if os_name != 'nt' and build_prefix:
+# Virtual environments using the build directory Python still keep their prefix.
+if not venv_prefix and os_name != 'nt' and build_prefix:
     prefix = config.get('prefix') or PREFIX
     exec_prefix = config.get('exec_prefix') or EXEC_PREFIX or prefix
 
@@ -788,8 +796,8 @@ def search_up(prefix, *landmarks, test=isfile):
 config['base_executable'] = base_executable
 config['prefix'] = prefix
 config['exec_prefix'] = exec_prefix
-config['base_prefix'] = base_prefix or prefix
-config['base_exec_prefix'] = base_exec_prefix or exec_prefix
+config['base_prefix'] = base_prefix
+config['base_exec_prefix'] = base_exec_prefix
 
 config['platlibdir'] = platlibdir
 # test_embed expects empty strings, not None